Method for the establishment of a crack resistant epoxy paint coat and paint compositions suitable for said method

ABSTRACT

The present invention relates to a method for the establishment of a crack resistant epoxy paint coat and paint compositions suitable for said method. The method is developed for use in ballast tanks e.g. a ballast tank of a vessel. The method involves the steps: (i) applying a paint composition comprising an epoxy-based binder system onto the surface thereby forming a curable paint film on the surface, and (ii) allowing the curable paint film to cure thereby forming the epoxy paint coat. The paint composition has a viscosity of at the most 140 KU, when ready to be applied. The paint composition comprises 35-80% by solids volume of the paint of an epoxy-based binder system having a ratio between the hydrogen equivalents and the epoxy equivalents in the range of 20:100 to 120:100. The paint composition furthermore comprises 0.5-30% by solids volume of the paint of one or more fibers. The fibers have an average length, of at the most 250 μm.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.14/320,063, now U.S. Pat. No. 9,080,062, filed on Jun. 30, 2014, whichis a Division of U.S. application Ser. No. 11/920,098, now U.S. Pat. No.8,945,680, filed on Nov. 8, 2007, which is the National Phase of PCTInternational Application No. PCT/DK2006/000249 filed on May 11, 2006,which claims the benefit under 35 U.S.C. §119(a) to Patent Application05388042.3, filed in European Patent Office on May 12, 2005, all ofwhich are hereby expressly incorporated by reference into the presentapplication.

FIELD OF THE INVENTION

The present invention relates to a method for the establishment of acrack resistant epoxy paint coat at the surface represented by theinterior of the angles formed between structural elements of aballast-tank of a partly or fully submersible structure. The presentinvention provides improved crack resistance of such an epoxy paint coatby incorporation of specific types of fibres.

BACKGROUND OF THE INVENTION

Existing epoxy products for coating a ballast-tank of a partly or fullysubmersible structure, such as a vessel or a semi submersible oil rig,show relatively high crack susceptibility when applied in extreme highdry film thickness. Cracks may occur during launch or during service inplaces with too high dry film thickness. Too high dry film thickness isespecially observed in association with the interior of the anglesformed between the structural elements, where the shape of the surfaceis such that a paint film with even thickness is seldom achieved.Existing epoxy products are typically specified in a total dry filmthickness of 250-500 μm, but in association with the interior of theangles formed between the structural elements there is a risk of gettingfar higher dry film thicknesses than specified. Too high coatingthickness, often exceeding normal acceptance limits, causes high curingshrinkage stress and may enhance cracking.

The factors leading to cracking of ballast tank coatings are studied inrecent articles by Askheim et al. (“Why do paints crack. Ballast tankcoating study focusing on brittleness and loss of flexibility”Protective Coating Europe, March 2001, pp 49-55) and Lim et al. (“StressAnalysis and Evaluation of Cracks Developed on the Coatings for WeldedJoints of Water Ballast Tanks” Paper presented at “Corrosion 2005”,Houston, USA).

The epoxy coat in a ballast tank is exposed to many stress inducingenvironmental effects, E.g. special environmental effects in ballasttanks of vessels include elevated temperature on areas, such asbulkheads adjacent to cargo holds and engine rooms, cyclic sun-heatingunderneath the main deck, water sloshing, reverse impacts from heavyloading equipment, and hydrostatic pressure changes fromballasting/de-ballasting cycles. The environmental effects give specialdemands to the flexibility and cracking resistance of an epoxy coatapplied in the ballast tank of a partly or fully submersible structure.Cracks in the paint film will lead to corrosion due to the presence ofwater, typically sea water, when ballast is required.

The brittleness of the epoxy coat is believed to be related tolimitations in the flexibility of basic epoxy chemistry. The epoxidegroup can react with various curing agents. Epoxide groups can alsohomopolymerise with themselves to varying degrees. The end result is athree-dimensional network of long chain molecules with limitedflexibility. The flexibility varies with the type and amount of curingagent as well as type and amount of flexibilisers. If much more than thestoichiometric amount of curing agent is added to the epoxy resin, theflexibility is improved, but mechanical strength and anticorrosiveproperties are reduced.

JP 59-78267A discloses a coating composition comprised of an epoxyresin, a curing agent, an inorganic staple fiber and a coatingcompounding agent. The coating composition is mainly used for acorrosion-proofing coating at the inside and outside of steel pipes.

A method is required for the establishment of a crack resistant epoxypaint coat at the surface represented by the interior of the anglesformed between structural elements of a ballast tank of a partly orfully submersible structure.

SUMMARY OF THE INVENTION

Thus, the underlying problem for the present invention is to provide amethod for the establishment of a crack resistant epoxy paint coat atthe surface represented by the interior of the angles formed betweenstructural elements of a ballast tank of a partly or fully submersiblestructure, said method comprising:

-   -   (i) applying a paint composition comprising an epoxy-based        binder system onto said surface thereby forming a curable paint        film on said surface, and    -   (ii) allowing said curable paint film to cure thereby forming        the epoxy paint coat;

wherein the paint composition has a viscosity of at the most 140 KU andcomprises

-   -   35-80% by solids volume of the paint of an epoxy-based binder        system having a ratio between the hydrogen equivalents and the        epoxy equivalents in the range of 20:100 to 120:100, and    -   0.5-30% by solids volume of the paint of one or more fibres        selected from the group consisting of natural inorganic fibres,        synthetic inorganic fibres, natural organic fibres, synthetic        organic fibres, and metallic fibres, said fibres having an        average length, of at the most 250 μm.

The present invention also relates to paint compositions as such.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a portion of a ballast tank and illustrates the surfacerepresented by the interior of the angles formed between structuralelements of the ballast-tank. For simplification stiffening memberstypically present in a ballast tank are not included in FIG. 1.

FIG. 2 illustrates the high dry film thickness of the epoxy paint coatthat is prone to arise due to the shape of the surface of aballast-tank.

DETAILED DESCRIPTION OF THE INVENTION

It has now been found that by applying an epoxy paint comprising fibresat the surface represented by the interior of the angles formed betweenthe structural elements of a ballast-tank of a partly or fullysubmersible structure, a crack resistant epoxy paint coat isestablished.

More specific, the invention relates to a method for the establishmentof a crack resistant epoxy paint coat at the surface represented by theinterior of the angles formed between structural elements of a ballasttank of a partly or fully submersible structure.

When used herein, the term “interior of the angles formed betweenstructural elements of a ballast tank” is intended to mean the surfaceextending 20 cm from both sides of the junction between structuralelements (e.g. metal plates) forming the inner surface of a ballast tankand representing an angle of between 45° to 140°. At the surfacerepresented by the interior of the angles formed between the structuralelements there is a problem with too high dry film thickness that mayresult in cracking.

Examples of junctions between structural elements forming the innersurface of a ballast tank and representing an angle of between 45° to140° include, but are not limited to, junctions between vertical sides,junctions between vertical sides and the top of a ballast tank,junctions between vertical sides and the bottom of a ballast tank andjunctions between vertical sides and stiffening members of a ballasttank.

The interior of the angles formed between structural elements of aballast tank is illustrated schematically in FIG. 1. Referring to FIG. 1the surface (A), the hatched area extending 20 cm from both sides of thejunctions between the vertical sides (I, II, III), between the verticalsides (I, II, III) and the tank top (IV) and between the vertical sides(I, II, III) and the tank bottom (V) is the interior of the anglesformed between the structural elements according to the abovedefinition.

The problem with too high dry film thickness is illustratedschematically in FIG. 2. FIG. 2 is a cross cut of a part of the surface(A) of FIG. 1 after application of the epoxy paint coat (E).

Structural elements of a ballast tank, e.g. metal plates, such as steelplates, are joined typically by welding. To construct a ballast tank, itis required that some of the structural elements are joined to form aninterior angle of 45° to 140°.

When used herein, the term “structural elements of a ballast tank” isintended to include sides, top, bottom and stiffening members of aballast tank. Examples of stiffening members are longitudinals, girdersand stringers. Such stiffening members are well known to the personskilled in the art and detailed examples are given in “Guidance manualfor tanker structures”, Tanker Structure Co-operative Forum. Witherby,London 1997, FIG. 1.1.

Examples of partly or fully submersible structures are vessels(including but not limited to boats, ocean liners, tankers, containerships and other cargo ships, submarines and naval vessels of all types)or semi submersible oil rigs etc.

The method further comprises the steps:

-   -   (i) applying a paint composition comprising an epoxy-based        binder system onto said surface thereby forming a curable paint        film on said surface, and    -   (ii) allowing said curable paint film to cure thereby forming        the epoxy paint coat;

The paint composition may be applied by means of any of the usualtechniques used within the paint field. Preferred application techniquesare spraying, e.g. airless spraying, and by means of a brush or aroller.

The method of the invention is intended to include applications wherethe epoxy paint is applied both to the surface represented by theinterior of the angles formed between the structural elements and toother surfaces of the ballast-tank. The epoxy paint may be applied onthe whole surface of the ballast-tank or only on parts of the surface,as long as parts of the surface applied include parts of the surfacerepresented by the interior of the angles formed between the structuralelements.

Paint Composition to be Used in the Method.

The paint composition to be used in the method of the present inventionis a film-forming paint composition, i.e. the combination of the paintconstituents should make it possible to prepare a film of substantiallyuniform thickness.

The paint compositions to be used in the method of the present inventionneed to be applicable by spray or brush opposed to pastes or similarproducts. It should therefore be understood that the paint compositionsto be used in the method of the present invention have a viscosity of atthe most 140 Krebs Unit (KU) at the application temperature. Theviscosity is determined just after the paint composition has been mixedand is ready to be applied. The viscosity is determined according toASTM D562-01 with the modification that the temperature of the specimenis the application temperature.

Fibres

Generally, “fibres” is intended to cover any fibres within the groups ofnatural inorganic fibres, synthetic inorganic fibres, natural organicfibres, synthetic organic fibres, and metallic fibres, or mixturesthereof. Without being bound to any specific theory, it is, however,presently believed that natural inorganic fibres and synthetic inorganicfibres, in particular mineral fibres of these types, are especiallypreferred.

It is presently believed that the fibres to be used within the presentinvention should fulfil certain criteria with respect to dimensions inorder to provide the improved properties of the paints within thepresent invention. Thus, with respect to average length and averagethickness of the fibres which are added to the paint during manufactureof the paint or mixed with the paint before application, such fibreshave an average length, of at the most 250 μm and an average thicknessof 1-50 μm.

Preferred fibres are fibres having an average thickness of 1-25 μm andan average length, of at the most 250 μm, especially an average lengthof 25-250 μm and an average thickness of 1-25 μM, in particularly anaverage length of 50-250 μm (such as 50-170 μm) and an average thicknessof 2-10 μm. The preferred fibres furthermore have a ratio between theaverage length and the average thickness of at least 2, such as at least3 e.g. at least 5.

It should be noted that the term “length” refers to the greatestdimension of the fibre particle in question. The term “average” whenused in connection with length indicates that a certain variation of thelength of fibres exists within the distribution of the fibres used. Theterm “average thickness” also refers to the fibres in question, however,with regard to the distribution of fibres also taking into account thelongitudinal and cross-sectional variation with each individual fibre.

In order for a certain particle to be considered as a fibre within thepresent context, the ratio between the greatest dimension and thesmallest dimension perpendicular to the length dimension insubstantially all points along the longitudinal axis (the lengthdimension—longest dimension) should not exceed 2.5:1, preferably notexceed 2:1. Furthermore, the ratio between the longest dimension and thesecond smallest of the two shortest dimensions should be at least 2:1,preferably at least 5:1. Thus, fibres are characterised of having onelong dimension and two short dimension, where the long dimension islonger than the two short dimensions (typically by an order ofmagnitude, or even more), and the two short dimensions are substantiallyequal (of the same order of magnitude). For completely regular fibres,i.e. fibres having a cylindrical shape, it is evident how to determinethe “length” (longest dimension) and the two (identical) shortestdimensions. For more irregular fibres, it is believed that therelationship between the dimensions can be evaluated by the followinghypothetical experiment: A regular, right-angled box is constructedaround the fibre. The box is constructed so as to have the smallestpossible volume as it should fully comprise the fibre. To the extentthat the fibre is curved, it is (again hypothetically) assumed that thefibre is flexible so that the volume of the hypothetical box can beminimised by “straightening” the fibre. In order for the “fibre” to berecognised as so in the present context, the ratio between the twosmallest dimensions of the box should be at the most 2.5:1 (preferably2:1) and the ratio between the longest dimension of the box and thesecond smallest of the two smallest dimensions of the box should be atleast 2:1, preferably at least 5:1.

The above is given as a general guideline in order to exclude othertypes of particles which may be referred to as “fibres” but which dohave less satisfactory properties within the present invention. Inparticular, the term “fibre” is not intended to include so-calledinorganic “fibre” materials which are used as fillers (e.g. frayed typefillers with no well defined dimensions, such as asbestine), cf.Hawley's Condensed Chemical Dictionary, 11^(th) Ed., (Sax and Lewis,eds.), Van Nostrand Reinhold Company, New York, 1987, page 521. Neitherdoes “fibre” include flake type fillers, e.g. mica, flake shaped clayminerals, aluminium flakes or glass flakes cf. the definition above.With respect to “curved” fibres, it should be understood that the lengthdimension should be considered as the length along the curve defined bythe fibre.

The surface of the fibres may or may not have been modified (surfacetreated) by chemical or physical processes. Examples of suchmodification processes used to improve the beneficial effects of thefibres are carbonisation; silylation; surface oxidation; etching, suchas treatment with alkali metal hydroxide, treatment with hydrofluoricacid; coating; poly electrolytic entrapment in the porous surfacestructures; adsorption processes; hydrogen-bonding processes; cationicbonding processes; esterification; anionic bonding processes; etc. aswell as any modification processes included in the manufacturing of thefibres.

In an interesting embodiment, the fibres to be incorporated in thepaints are biodegradable under physiological conditions, especially inthe respiratory organs (the lungs) of mammals, especially humans. Thus,it is believed that especially interesting fibres are those which areable to biodegrade when present in a modified Gamble's solution asdefined in WO 96/14454, page 9. The degree of biodegradability shouldpreferably be at least 20 nm/day, such as at least 30 nm/day, inparticular at least 50 nm/day when tested as described in WO 96/14454.Examples of suitable biodegradable fibres are the ones described in WO96/14454 and WO 96/14274. A specific example thereof is the commerciallyavailable MS 600 Roxul 1000, ex. Lapinus Fibres BV (see below). Thebiodegradability is especially relevant for mineral fibres.

The fibres may, as it will be clear from the description of themanufacture processes further below, be added together with theremaining paint constituents before milling or the fibres may be addedafterwards. It can, however, be expected that the average length of thefibres will be somewhat reduced during the paint manufacture process(see further below), e.g. due to the applied shear forces and/or millingprocess. (Milling and intensive stirring is typically performed in orderto break up agglomerates of pigments and other particles in the paintcomposition). It is believed that the paint manufacture process shouldpreferably be performed so that the fibres in the ready-to-use painthave an average length corresponding to at least 75% of thepre-manufacture average length.

The concentration of the fibres is normally in the range of 0.5-30% bysolids volume of the paint, such as 0.5-20% by solids volume of thepaint. Especially relevant concentrations of fibres, depending upon thetype and size of the fibres, may be 2-20%, such as 3-18%, such as 5-15%by solids volume of the paint.

It should be understood that the above ranges refer to the total amountof fibres, thus, in the case where two or more fibre types are utilised,the combined amounts should fall within the above ranges.

Inorganic Fibres

Generally, “inorganic fibres” is intended to cover any fibres within thegroups of natural inorganic fibres, synthetic inorganic fibres, andmetallic fibres, or mixtures thereof. Without being bound to anyspecific theory, it is, however, presently believed that naturalinorganic fibres and synthetic inorganic fibres, in particular mineralfibres of these types, are especially preferred.

By mineral fibres should be understood fibres made using minerals asstarting materials. According to this definition, mineral fibres includeboth crystalline materials as well as amorphous materials formed by amelting process.

In the present invention, preferred inorganic fibres are inorganicfibres having an average thickness of 1-25 μm and an average length, ofat the most 250 μm, especially an average length of 25-250 μm and anaverage thickness of 1-25 μm, in particularly an average length of50-250 μm (such as 50-170 μm) and an average thickness of 2-20 μm (suchas 2-10 μm). The preferred inorganic fibres furthermore have a ratiobetween the average length and the average thickness of at least 2, suchas at least 5, preferably a ratio between the average length and theaverage thickness of at least 10, in particularly at least 15, such asat least 20.

Examples of inorganic fibres are carbide fibres, such as silicon carbidefibres, boron carbide fibres, niobium carbide fibres; nitride fibres,such as silicon nitride fibres; boron containing fibres, such as boronfibres, boride fibres; silicon-containing fibres, such as siliconfibres, alumina-boron-silica fibres, E-glass (non-alkalinealumoborosilicate) fibres, C-glass (non-alkaline or low-alkaline sodalime-alumoborosilicate) fibres, A-glass (alkaline soda lime-silicate)fibres, S-glass fibres, CEMFIL-glass fibres, ARG-glass fibres,mineral-glass fibres, non-alkaline magnesia alumosilicate fibres, quartzfibres, silicic acid fibres, silica fibres, high-silica fibres, aluminahigh-silica fibres, alumosilicate fibres, aluminium silicate fibres,magnesia alumosilicate fibres, soda borosilicate fibres, soda silicatefibres, polycarbosilane fibres, polytitanocarbosilane fibres,polysilazane fibres, hydridopolysilazane fibres, tobermorite fibres,samarium silicate fibres, wollastonite fibres, potassium aluminiumsilicate fibres; metal fibres, such as iron fibres, aluminium fibres,steel fibres, iron fibres, zinc fibres; carbon fibres, such as purecarbon fibres, graphite fibres, slagwool fibres, charcoal fibres;rockwool fibres, such as pure rockwool fibres and basalt rockwoolfibres; processed mineral fibres from mineral wool; volcanic rockfibres; attapulgite fibres; etc.; modified by any chemical or physicalprocesses; and any mixture thereof.

It is presently believed that one very interesting group of fibres isinorganic fibres, in particular mineral fibres. Particularly preferredexamples of such fibres are silicon-containing fibres; metal fibres;oxide fibres; carbon fibres; rockwool fibres; processed mineral fibresfrom mineral wool; volcanic rock fibres; wollastonite fibres;tobermorite fibres; attapulgite fibres.

At present, especially preferred are mineral fibres, such asmineral-glass fibres, wollastonite fibres, tobermorite fibres,attapulgite fibres, volcanic rock fibres, bauxite fibres, rockwoolfibres, and processed mineral fibres from mineral wool. Examples ofcommercially available mineral fibres which are believed to improve themechanical properties according to the invention are (average fibrelength in μm; average fibre thickness in μm):

0. CoatForce CF10, ex. Lapinus Fibres BV (The Netherlands), (125±25;7)

1. MS 600 Roxul 1000, ex. Lapinus Fibres BV (The Netherlands), volcanicrock fibre (125;5)

2. MS 610 Roxul 1000, ex. Lapinus Fibres BV (The Netherlands), (225;5.5)

3. FG 400/060, ex. Schwarzwalder Textil-Werke (Germany), E-glass(230;9-14)

4. FG 440/040, ex. Schwarzwalder Textil-Werke (Germany), E-glass(150;9-14)

5. Nyad G, ex. Nyco Minerals (USA), wollastonite (length/diameter ratio15:1)

6. Nyglos M15, ex. Nyco Minerals (USA), wollastonite (length/diameterratio 8:1)

7. Nyglos 8, ex. Nyco Minerals (USA), wollastonite (length/diameterratio 19:1)

8. RCF-160, ex. Sumitomo (Japan), C-glass (250;-)

9. Isofrax 1260C High Index, ex. Unifrax (United Kingdom) (-;2-3 μm)

Organic Fibres

Generally, “organic fibres” is intended to cover any fibres within thegroups of natural organic fibres and synthetic organic fibres. In thepresent invention, preferred organic fibres are organic fibres having anaverage thickness of 1-25 μM and an average length, of at the most 250μm, especially an average length of 25-250 μm and an average thicknessof 1-25 μm, in particularly an average length of 50-250 μm (such as50-170 μm) and an average thickness of 2-10 μm. The preferred organicfibres furthermore have a ratio between the average length and theaverage thickness of at least 2, such as at least 3 e.g. at least 5.

Examples of natural and synthetic organic fibres are aromatic polyamidefibres, such as poly(p-benzamide) fibres,poly(p-phenylene-terephthalamide) fibres,poly(p-phenylene-2,6-naphthalamide) fibres,poly(3,4′-diphenylether-terephthalamide) fibres,poly(p-phenylene-(p-benzamide)-terephthalamide) fibres,poly(p-benzhydrazide terephthalamide) fibres,poly(m-phenylene-isophthalamide) fibres,poly(N,N′-m-phenylene-bis(m-benzamide)-terephthalamide) fibres,poly(N,N′-m-phenylene-bis(m-benzamide)-2,6-naphthalamide) fibres,poly(N,N′-m-phenylene-bis(m-benzamide)-4,4′-biphenyl-dicarboxamide)fibres, poly(4,4′-bis(p-aminophenyl)-2,2′-bithiazole-isophthalamide)fibres, poly(2,5-bis(p-amino-phenyl)-1,3,4-oxa-diazole-isophthalamide)fibres, poly(4,4′-diaminobenzanilide-isophthalamide) fibres,poly(2-methyl-p-phenylene-2,6-naphthalamide) fibres,poly(2,6-dichloro-p-phenylene-2,6-naphthalamide) fibres; aromaticpolyhydrazide fibres, such as poly(terephthalic-m-phenylene-hydrazide)fibres, poly(terephthalic-hydrazide) fibres,poly(p-phenylene-N-methyl-hydrazide) fibres; aromatic polyester fibres,such aspoly(chloro-1,4-phenylene-ethylene-dioxy-4,4′-benzoate-co-terephthalate)fibres, poly(chloro-1,4-phenylene-4,4′-oxydibenzoate) fibres,poly(methyl-1,4-phenylene-4,4′-oxydibenzoate) fibres,poly(chlorophenylene-hexahydroterephthalate) fibres; aromaticpolyazomethine fibres, such aspoly(nitrilo-(2-methyl-1,4-phenylene)nitrilomethylidyne-1,4-phenylenemethylidyne)fibres; aromatic polyimide fibres, such as aromatic polypyromellitimidefibres, aromatic polytrimellitimide fibres, polyester-imide fibres,poly(4,4′-diphenyl-ether-pyromellitimide) fibres; aromatic heterocyclicpolymeric fibres, such as polybenzimidazole fibres, such aspoly-(2,2′-(m-phenylene)-5,5′-bibenzimidazole) fibres, polybenzothiazolefibres, such as poly(2-(1,4-phenylene)-2′-(6,6′-bibenzothiazole)) fibresand poly(2-(1,3-phenylene)-2′-(6,6′-bibenzothiazole)) fibres,polybenzoxazole fibres, such aspoly((1,7-dihydrobenzo(1,2-d:4,5-d′)dioxazole-2,6-diyl)-1,4-phenylene)fibres and poly((benzo(1,2-d:4,5-d′)bisoxazol-2,6-diyl)-1,4-phenylene)fibres, polyoxadiazole fibres, such as polyarylene-1,3,4-oxadiazolefibres; cellulose fibres, such as α-cellulose fibres, β-cellulosefibres, mineral cellulose fibres, methylcellulose fibres, cellucottonfibres, regenerated cellulose (rayon) fibres, cellulose acetate fibres,jute fibres, cotton fibres, linen fibres, ramie fibres, sisal fibres,heme fibres, flax fibres, cyanoethylated cellulose fibres, acetylatedcellulose fibres; wood fibres, such as pine, spruce and fir wood fibres,lignin fibres and fibres of lignin derivatives; rubber fibres and fibresof derivatives of rubber; polyolefin fibres, such as polyethylenefibres, polypropylene fibres, polytetrafluoroethylene fibres,polybutadiene fibres; polyacetylene fibres; polyester fibres; acrylicfibres and modified acrylic fibres, such as acrylic acid fibres,styrol/acrylate fibres; acrylonitrile fibres, such as acrylonitrilefibres and polyacrylonitrile fibres; elastomeric fibres; protein fibres,such as casein fibres, maize protein fibres, soybean protein fibres,groundnut protein fibres; alginate fibres; poly(ethylene terephthalate)fibres; polyvinyl alcohol fibres; aliphatic polyamide fibres, such asnylon fibres e.g. nylon 6.6 fibres, nylon 6 fibres, nylon 6.10 fibres;poly(phenylene sulphide) fibres; polyvinylchloride fibres;polychloroethene fibres; poly(bisbenzimidazobenzophenanthrolin) fibres;polyoxymethylene fibres; polyurethane fibres; vinyl polymeric fibres;viscose fibres; etc.; modified by any chemical or physical processes;and any mixture thereof.

Examples of commercially available organic fibres which are believed toimprove the mechanical properties according to the invention are(average fibre length in μm; average fibre thickness in μm):

10. Arbocel BE 600/30, ex. 3. Rettenmaier & Söhne GmbH. (Germany),natural cellulose fibre (40;20)

11. Lignocel C 120, ex. J. Rettenmaier & Söhne GmbH (Germany), woodfibre (70-150;-)

12. PAN60 ex. F.H. Wrigley Ltd (United Kingdom), polyacrylonitrile flockfibre, (max 250;15)

It is, however, also presently believed that some organic fibres can beespecially advantageous within the present invention. Particularlypreferred examples of such fibres are aromatic polyamide fibres;aromatic polyester fibres; aromatic polyimide fibres; cellulose fibres;cotton fibres; wood fibres; rubber fibres and fibres of derivatives ofrubber; polyolefin fibres (e.g. polypropylene fibres); polyacetylenefibres; polyester fibres; acrylic fibres and modified acrylic fibres;acrylonitrile fibres (e.g. preoxidised acrylonitrile fibres);elastomeric fibres; protein fibres; alginate fibres; poly(ethyleneterephthalate) fibres; polyvinyl alcohol fibres; aliphatic polyamidefibres; polyvinylchloride fibres; polyurethane fibres; vinyl polymericfibres; and viscose fibres. Presently even more preferred examples ofsuch fibres are polyethylene fibres, polypropylene fibres, cottonfibres, cellulose fibres, polyacrylonitrile fibres, preoxidisedpolyacrylonitrile fibres, wood fibres and polyester fibres.

It is presently believe that a particularly interesting group of organicfibres is cellulose fibres, wood fibres and polyacrylonitrile fibres.

Epoxy-Based Binder System

The term “epoxy-based binder system” should be construed as thecombination of the one or more epoxy resins, one or more curing agents,any reactive epoxy diluents and any reactive acrylic modifiers.

The epoxy-based binder system is one of the most important constituentsof the paint composition, in particular with respect to theanticorrosive properties. Besides the anticorrosive properties, it isrelevant that the epoxy paint coat resulting from the application of thepaint composition is flexible.

The epoxy-based binder system comprises one or more epoxy resinsselected from aromatic or non-aromatic epoxy resins (e.g. hydrogenatedepoxy resins), containing more than one epoxy group per molecule, whichis placed internally, terminally, or on a cyclic structure, togetherwith one or more suitable curing agents to act as cross-linking agents.Combinations with reactive diluents from the classes mono functionalglycidyl ethers or esters of aliphatic, cycloaliphatic or aromaticcompounds can be included in order to reduce viscosity and for improvedapplication and physical properties. The binder system can also includereactive acrylic modifiers, such as acrylate monomers and oligomerscomprising at least two alpha, beta unsaturated carbonyl groups,reacting with the one or more curing agents via a Michael-type additionreaction.

Suitable epoxy-based binder systems are believed to include epoxy andmodified epoxy resins selected from bisphenol A, bisphenol F, Novolacepoxies, non-aromatic epoxies, cycloaliphatic epoxies, glycidyl estersand epoxy functional acrylics or any combinations hereof. Examples ofsuitable commercially available epoxy resins are:

Epikote 828, ex. Resolution Performance Products (The Netherlands),bisphenol A type

Araldite GY 250, ex. Huntsman Advanced Materials (Switzerland),bisphenol A type

Epikote 1004, ex. Resolution Performance Products (Germany), bisphenol Atype

DER 664-20, ex. Dow Chemicals (Germany), bisphenol A type

Epikote 1001 X 75, ex. Resolution Performance Products (TheNetherlands), bisphenol A type

Araldite GZ 7071X75BD, ex. Huntsman Advanced Materials (Germany),bisphenol A type

DER 352, ex. Dow Chemicals (Germany), mixture of bisphenol A andbisphenol F

Epikote 232, ex. Resolution Performance Products (The Netherlands),mixture of bisphenol A and bisphenol F

Epikote 862, ex. Resolution Performance Products (The Netherlands),bisphenol F type

DEN 438-X 80, ex. Dow Chemical Company (USA), epoxy novolac

Epikote 154, ex. Resolution Performance Products (The Netherlands),epoxy novolac

The epoxy-based binder system comprises one or more curing agentsselected from compounds or polymers comprising at least two reactivehydrogen atoms linked to nitrogen.

Suitable curing agents are believed to include amines or aminofunctional polymers selected from aliphatic amines and polyamines (e.g.cycloaliphatic amines and polyamines), polyamidoamines, polyoxyalkyleneamines (e.g. polyoxyalkylene diamines), aminated polyalkoxyethers (e.g.those sold commercially as “Jeffamines”), alkylene amines (e.g. alkylenediamines), aralkylamines, aromatic amines, Mannich bases (e.g. thosesold commercially as “phenalkamines”), amino functional silicones orsilanes, and including epoxy adducts and derivatives thereof. Examplesof suitable commercially available curing agents are:

Cardolite NC-541, ex. Cardanol Chemicals (USA), Mannich base

Cardolite Lite 2001, ex. Cardanol Chemicals (USA), Mannich base

Sunmide CX-105X, ex. Sanwa Chemical Ind. Co. Ltd. (Singapore), Mannichbase

Epikure 3140 Curing Agent, ex. Resolution Performance Products (USA),polyamidoamine

SIQ Amin 2030, ex. SIQ Kunstharze GmbH (Germany), polyamidoamine

Epikure 3115X-70 Curing Agent, ex. Resolution Performance Products(USA), polyamidoamine

SIQ Amin 2015, ex. SIQ Kunstharze GmbH (Germany), polyamidoamine

Polypox VH 40309/12, ex. Ulf Prümmer Polymer-Chemie GmbH (Germany),polyoxyalkylene amine

CeTePox 1490 H, ex. CTP Chemicals and Technologies for Polymers(Germany), polyoxyalkylene amine

Epoxy hardener MXDA, ex. Mitsubishi Gas Chemical Company Inc (USA),aralkyl amine

Diethylaminopropylamine, ex. BASF (Germany), aliphatic amine

Gaskamine 240, ex. Mitsubishi Gas Chemical Company Inc (USA), aralkylamine

Cardolite Lite 2002, ex. Cardanol Chemicals (USA), Mannich base

Aradur 42 BD, ex. Huntsman Advanced Materials (Germany), cycloaliphaticamine

Isophorondiamin, ex. BASF (Germany), cycloaliphatic amine

Epikure 3090 Curing Agent, ex. Resolution Performance Products (USA),polyamidoamine adduct with epoxy

Crayamid E260 E90, ex. Cray Valley (Italy), polyamidoamine adduct withepoxy

Aradur 943 CH, ex. Huntsman Advanced Materials (Switzerland), alkyleneamine adduct with epoxy

Aradur 863 XW 80 CH, ex. Huntsman Advanced Materials (Switzerland),aromatic amine adduct with epoxy

Preferred epoxy-based binder systems comprises a) one or more epoxyresins selected from bisphenol A, bisphenol F and Novolac; and b) one ormore curing agents selected from Mannich Bases, polyamidoamines,polyoxyalkylene amines, alkylene amines, aralkylamines, polyamines, andadducts and derivatives thereof.

Especially preferred epoxy-based binder systems comprise one or morebisphenol A epoxy resins and one or more curing agents selected fromMannich Bases, polyamidoamines and adducts and derivatives thereof.

Preferably, the epoxy resin has an epoxy equivalent weight of 100-2000,such as 100-1500, e.g. 150-1000, such as 150-700.

Especially preferred epoxy-based binder systems comprise one or morebisphenol A epoxy resins having an epoxy equivalent weight of 150-700and one or more polyamidoamine or adducts and derivatives thereof.

Preferred epoxy-based binder systems are ambient curing binder systems.

In the paint composition, the total amount of epoxy-based binder systemis in the range of 15-80%, such as 35-80%, e.g. 40-75% by solids volumeof the paint.

Without being bound to any particular theory, it is believed that theselection of the ratio between the hydrogen equivalents of the one ormore curing agents and the epoxy equivalents of the one or more epoxyresins plays a certain role for the performance of the coatingcomposition.

When used herein, the term “hydrogen equivalents” is intended to coveronly reactive hydrogen atoms linked to nitrogen.

The number of “hydrogen equivalents” in relation to the one or morecuring agents is the sum of the contribution from each of the one ormore curing agents. The contribution from each of the one or more curingagents to the hydrogen equivalents is defined as grams of the curingagent divided by the hydrogen equivalent weight of the curing agent,where the hydrogen equivalent weight of the curing agent is determinedas: grams of the curing agent equivalent to 1 mole of active hydrogen.For adducts with epoxy resins the contribution of the reactants beforeadductation is used for the determination of the number of “hydrogenequivalents” in the epoxy-based binder system.

The number of “epoxy equivalents” in relation to the one or more epoxyresins is the sum of the contribution from each of the one or more epoxyresins. The contribution from each of the one or more epoxy resins tothe epoxy equivalents is defined as grams of the epoxy resin divided bythe epoxy equivalent weight of the epoxy resin, where the epoxyequivalent weight of the epoxy resin is determined as: grams of theepoxy resin equivalent to 1 mole of epoxy groups. For adducts with epoxyresins, the contribution of the reactants before adductation is used forthe determination of the number of “epoxy equivalents” in theepoxy-based binder system.

It should be understood that if the epoxy-based binder system containsreactive acrylic modifiers then the number of “epoxy equivalents” is tobe increased accordingly. E.g. if the epoxy-based binder system containsan acrylate oligomer comprising alpha, beta unsaturated carbonyl groupsthen the number of “alpha, beta unsaturated carbonyl group equivalents”are to be added to the epoxy equivalents of the one or more epoxy resinsfor the purpose of establishing the ratio between the hydrogenequivalents of the one or more curing agents and the epoxy equivalentsof the one or more epoxy resins.

Preferably, the ratio between the hydrogen equivalents of the one ormore curing agents and the epoxy equivalents of the one or more epoxyresins is in the range of 20:100 to 120:100.

Especially preferred epoxy-based binder systems for use in ballast tankcoatings have a ratio between the hydrogen equivalents of the one ormore curing agents and the epoxy equivalents of the one or more epoxyresins in the range of 60:100 to 120:100, such as 70:100 to 110:100.

Other Constituents

It has previously been common to include coal-tar in epoxy paintcompositions. However due to a suspected carcinogenic effect it ispreferred that epoxy paint compositions do not contain coal-tar. Thepresence of coal-tar furthermore makes it difficult to make lightshades. Light shades are preferred in ballast-tanks to facilitateinspection for possible damages to the paint film. Thus, in a preferredembodiment the coating composition comprises 0% by solids volume of thepaint of coal-tar.

The paint composition may comprise plasticizers. Examples ofplasticizers are hydrocarbon resins, phthalates and benzyl alcohol. Inone preferred embodiment, the paint composition comprises a hydrocarbonresin as plasticizer.

In the paint composition, the total amount of plasticizers (e.g.hydrocarbon resins) may be in the range of 0-30%, such as 0-25% bysolids volume of the paint, preferably 1-25%, such as 1-20% by solidsvolume of the paint.

The paint composition may comprise other paint constituents as will beapparent for the person skilled in the art. Examples of such paintconstituents are pigments, fillers, additives (e.g. epoxy accelerators,surfactants, wetting agents and dispersants, de-foaming agents,catalysts, stabilizers, corrosion inhibitors, coalescing agents,thixothropic agents (such as polyamide waxes), anti-settling agents anddyes).

In the paint composition, the total amount of pigments and fillers maybe in the range of 0-50%, such as 5-50% by solids volume of the paint,preferably 10-45%, such as 10-40% by solids volume of the paint.

It is envisaged that certain pigments and fillers have a beneficialeffect on the anticorrosive properties. Examples are aluminium pigments,zinc phosphate and mica. In one preferred embodiment, the paintcomposition comprises 0-10% by solids volume of the paint of aluminiumpigments, preferably 1-7%, such as 2-6% by solids volume of the paint.In an alternative embodiment, the composition comprises at the most 10%by dry weight of the paint of aluminium pigments.

In the paint composition, the total amount of additives may be in therange of 0-10%, such as 0.1-8% by solids volume of the paint.

The paint composition may comprise epoxy accelerators. Examples aresubstituted phenols, such as 2,4,6-tris (dimethylamino methyl) phenol,p-tert-butylphenol, nonyl phenol etc.

The paint composition typically comprises a solvent or solvents.Examples of solvents are alcohols, such as water, methanol, ethanol,propanol, isopropanol, butanol, isobutanol and benzyl alcohol;alcohol/water mixtures, such as ethanol/water mixtures; aliphatic,cycloaliphatic and aromatic hydrocarbons, such as white spirit,cyclohexane, toluene, xylene and naphtha solvent; ketones, such asmethyl ethyl ketone, acetone, methyl isobutyl ketone, methyl isoamylketone, diacetone alcohol and cyciohexanone; ether alcohols, such as2-butoxyethanol, propylene glycol monomethyl ether and butyl diglycol;esters, such as methoxypropyl acetate, n-butyl acetate and 2-ethoxyethylacetate; and mixtures thereof.

Depending on the application technique, it is desirable that the paintcomprises solvent(s) so that the solids volume ratio (SVR—ratio betweenthe volume of solid constituents to the total volume) is in the range of30-100%, preferably 50-100%, in particular 55-100% e.g. 60-100%.

SVR is determined according to ISO 3233 or ASTM D 2697 with themodification that drying is carried out at 20° C. and 60% relativehumidity for 7 days instead of drying at higher temperatures.

Preparation of the Paint Composition

The paint may be prepared by any suitable technique that is commonlyused within the field of paint production. Thus, the variousconstituents may be mixed together using a high speed disperser, a ballmill, a pearl mill, a three-roll mill etc. The paints according to theinvention may be filtrated using bag filters, patron filters, wire gapfilters, wedge wire filters, metal edge filters, EGLM turnoclean filters(ex. Cuno), DELTA strain filters (ex. Cuno), and Jenag Strainer filters(ex. Jenag), or by vibration filtration.

The paint composition to be used in the method of the invention isprepared by mixing two or more components e.g. two pre-mixtures, onepre-mixture comprising the one or more epoxy resins and one pre-mixturecomprising the one or more curing agents. It should be understood thatwhen reference is made to the paint composition, it is the mixed paintcomposition ready to be applied. Furthermore, all amounts stated as % bysolids volume of the paint should be understood as % by solids volume ofthe mixed paint composition ready to be applied.

Novel Paint Compositions

It is believed that at least some of the epoxy paint compositionsdefined herein for the method of the invention is novel as such. Thus, afurther aspect of the invention relates to a paint composition, saidpaint composition having a viscosity of at the most 140 KU at 30° C. andcomprising:

-   -   35-80% by solids volume of the paint of an epoxy-based binder        system having a ratio between the hydrogen equivalents and the        epoxy equivalents in the range of 20:100 to 120:100, and    -   0.5-30% by solids volume of the paint of one or more fibres        selected from the group comprising natural inorganic fibres,        synthetic inorganic fibres, natural organic fibres, synthetic        organic fibres, and metallic fibres, said fibres having an        average length, of at the most 250 μm.

Yet a further aspect of the present invention relates to a paintcomposition having a viscosity of at the most 140 KU at 30° C. andcomprising:

-   -   35-80% by solids volume of the paint of an epoxy-based binder        system having a ratio between the hydrogen equivalents and the        epoxy equivalents in the range of 70:100 to 110:100, and    -   0.5-30% by solids volume of the paint of one or more fibres        selected from the group comprising natural inorganic fibres,        synthetic inorganic fibres, natural organic fibres, synthetic        organic fibres, and metallic fibres, said fibres having an        average length, of at the most 250 μm.

In one interesting embodiment hereof, the coating composition comprises1-25% by solids volume of the paint of a plasticizer.

In a more specific variant hereof, the coating composition comprises:

-   -   40-75% by solids volume of the paint of an epoxy-based binder        system having a ratio between the hydrogen equivalents and the        epoxy equivalents in the range of 70:100 to 110:100,    -   0.5-30% by solids volume of the paint of one or more fibres        selected from the group comprising natural inorganic fibres,        synthetic inorganic fibres, natural organic fibres, synthetic        organic fibres, and metallic fibres, said fibres having an        average length, of at the most 250 μm, and    -   1-20% by solids volume of the paint of a plasticizer.

Yet a further aspect of the present invention relates to a paintcomposition having a viscosity of at the most 140 KU at 30° C. andcomprising:

-   -   35-80% by solids volume of the paint of an epoxy-based binder        system having a ratio between the hydrogen equivalents and the        epoxy equivalents in the range of 70:100 to 110:100,    -   0.5-30% by solids volume of the paint of one or more fibres        selected from the group comprising natural inorganic fibres,        synthetic inorganic fibres, natural organic fibres, synthetic        organic fibres, and metallic fibres, said fibres having an        average length, of at the most 250 μm, and    -   1-7% by solids volume of the paint of aluminium pigments.

Another aspect of the present invention relates to a paint compositionhaving a viscosity of at the most 140 KU at 30° C. and comprising:

-   -   35-80% of an epoxy-based binder system comprising one or more        novolac epoxy resins and one or more curing agents selected from        alkylene amines and aralkyl amines, said epoxy-based binder        system having a ratio between the hydrogen equivalents and the        epoxy equivalents in the range of 20:100 to 50:100, and    -   0.5-30% by solids volume of the paint of one or more fibres        selected from the group comprising natural inorganic fibres,        synthetic inorganic fibres, natural organic fibres, synthetic        organic fibres, and metallic fibres, said fibres having an        average length, of at the most 250 μm.

Another aspect of the present invention relates to a paint compositionhaving a viscosity of at the most 140 KU at 30° C. and comprising:

-   -   15-80%, such as 35-80%, e.g. 40-75%, by solids volume of the        paint of an epoxy-based binder system having a ratio between the        hydrogen equivalents and the epoxy equivalents in the range of        20:100 to 120:100, such as 60:100 to 120:100 or 20:100 to        50:100,    -   0.5-30%, such as 2-20%, e.g. 3-18% by solids volume of the paint        of fibres, said fibres having an average length, of at the most        250 μm,    -   5-50%, such as 10-45%, e.g. 10-40% by solids volume of the paint        of fillers and pigments,    -   0-30% or 1-25%, such as 1-20% by solids volume of the paint of        plasticizers, and    -   0-10% or 0.1-8% by solids volume of the paint of additives.

In a more specific variant hereof, the coating composition consist of:

-   -   35-80%, such as 40-75%, by solids volume of the paint of an        epoxy-based binder system having a ratio between the hydrogen        equivalents and the epoxy equivalents in the range of 20:100 to        120:100, such as 60:100 to 120:100 or 20:100 to 50:100,    -   0.5-30%, such as 2-20%, e.g. 3-18% by solids volume of the paint        of fibres, said fibres having an average length, of at the most        250 urn,    -   5-50%, such as 10-45%, e.g. 10-40% by solids volume of the paint        of fillers and pigments,    -   0-30% or 1-25%, such as 1-20% by solids volume of the paint of        plasticizers,    -   0-10% or 0.1-8% by solids volume of the paint of additives, and    -   one or more solvents.

With respect to the above mentioned aspects, the selection of fibres,epoxy-based binder system and other constituents are essentially asdescribed and exemplified herein above.

Among the novel epoxy paint compositions defined herein for the methodof the invention, it is contemplated that there are some that mayadvantageously be used for other methods than the method of the presentinvention. It is envisaged that such paint compositions mayadvantageously be used in methods for establishing a crack resistantepoxy paint coat in for example cargo holds and liquid storage tanks,such as water tanks and chemical tanks, and for establishing crackresistant epoxy paint coat on for example Rail cars, Containers,Bridges, cranes and Wind turbines.

Liquid Storage Tank

In one preferred embodiment, a novel epoxy paint composition definedherein for the method of the invention is used in a method forestablishing a crack resistant epoxy paint coat on the interior surfaceof a liquid storage tank, said method comprising

-   -   (i) applying a paint composition comprising an epoxy-based        binder system onto the surface of the interior of a liquid        storage tank thereby forming a curable paint film on said        surface, and    -   (ii) allowing said curable paint film to cure thereby forming        the epoxy paint coat;

wherein the paint composition has a viscosity of at the most 140 Ku andcomprises:

-   -   35-80% by solids volume of the paint of an epoxy-based binder        system having a ratio between the hydrogen equivalents and the        epoxy equivalents in the range of 20:100 to 120:100, and    -   0.5-30% by solids volume of the paint of one or more fibres        selected from the group comprising natural inorganic fibres,        synthetic inorganic fibres, natural organic fibres, synthetic        organic fibres, and metallic fibres, said fibres having an        average length, of at the most 250 μm.

Examples of liquid storage tanks where such a method may advantageouslybe used are storage tanks for Food oil; Light oil; Palm oil; Lube oil;Vegetable oil; crude oil and refined fuel products, such as Gasoline,Heavy fuel, Jet fuel, Refinery fuel, Unleaded gasoline, Diesel,Kerosene; Gas, such as LPG (liquefied petroleum gas), LNG (liquefiednatural gas), Butan, Nitrogen; Water, such as Process water,Demineralised water, Waste water, Potable water; organic solvents, suchas Naphtha, Methanol, Ethylene glycol, Ethylbenzene, Aromatics,Benzene/cyclohexane mixtures, benzene/toluene/xylene mixtures;Chemicals, such as Sodium hydroxide, Asphalt, Propylene, Glycerine,Ammonia, Ethylene. The examples of liquid storage tanks include bothstationary tanks as well as movable liquid storage tanks e.g. liquidstorage tanks on vessels.

Some types of liquid storage tanks require a high degree of chemicalresistance. To ensure a high degree of chemical resistance, epoxy paintcompositions used in a method for establishing a crack resistant epoxypaint coat in a liquid storage tank where a high degree of chemicalresistance is required, should preferably comprise one or more novolacepoxy resins and/or bisphenol F resins.

In one interesting embodiment hereof, a novel epoxy paint compositiondefined herein for the method of the invention is used in a method forestablishing a crack resistant epoxy paint coat in liquid storage tankswhere a high degree of chemical resistance is required, said methodcomprising:

-   -   (i) applying a paint composition comprising an epoxy-based        binder system onto the surface of the interior of a liquid        storage tank thereby forming a curable paint film on said        surface, and    -   (ii) allowing said curable paint film to cure thereby forming        the epoxy paint coat;

wherein the paint composition has a viscosity of at the most 140 KU andcomprises:

-   -   35-80% of an epoxy-based binder system comprising one or more        novolac epoxy resins and one or more curing agents selected from        alkylene amines and aralkyl amines, said epoxy-based binder        system having a ratio between the hydrogen equivalents and the        epoxy equivalents in the range of 20:100 to 50:100, and    -   0.5-30% by solids volume of the paint of one or more fibres        selected from the group comprising natural inorganic fibres,        synthetic inorganic fibres, natural organic fibres, synthetic        organic fibres, and metallic fibres, said fibres having an        average length, of at the most 250 μm.

The invention also relates to similar methods for establishing a crackresistant epoxy paint coat on rail cars, containers, bridges, cranes,wind turbines etc.

EXAMPLES Materials

Fibre 1: MS 600 Roxul 1000, ex. Lapinus Fibres BV (The Netherlands)

Fibre 2: Arbocel BE600/30 PU, ex. J. Rettenmaier & Söhne Gmbh (Germany)

Fibre 3: Nyglos 8, ex. Nyco Minerals (USA)

Fibre 4: PAN60 polyacrylonitrile flock fibre, ex. F.H. WrigleyLtd/Wrigley Fibres (United Kingdom)

HEMPADUR 45143-11480 is an anticorrosive epoxy paint from Hempel A/Sthat may be specified for ballast tanks. The epoxy-based binder systemof 45143-11480 consists of: Bisphenol A epoxy resins having epoxyequivalent weights within the interval 150-700 and a polyamidoamine ascuring agent. HEMPADUR 45143-11480 furthermore comprises a modifiedaromatic hydrocarbon resin as plasticizer (the amount is within theinterval 1-25% by solids volume of the paint). The viscosity is lessthan 140 KU at 30° C. The ratio between the hydrogen equivalents of theone or more curing agents and the epoxy equivalents of the one or moreepoxy resins is in the range of 70:100 to 110:100. The ratio between thehydrogen equivalents of the one or more curing agents and the epoxyequivalents of the one or more epoxy resins is not affected when addingfibres 1-4.

HEMPADUR 15500-50900 is an anticorrosive epoxy paint from Hempel A/Sthat may be specified for ballast tanks. The epoxy-based binder systemof HEMPADUR 15500-50900 consists of: A novolac epoxy resin having anepoxy equivalent weight within the interval 150-700, bisphenol A epoxyresins having epoxy equivalent weights within the interval 150-700 andas curing agents an alkylene amine and an aralkyl amine. The viscosityis less than 140 KU at 30° C. The ratio between the hydrogen equivalentsof the one or more curing agents and the epoxy equivalents of the one ormore epoxy resins is in the range of 20:100 to 50:100. The ratio betweenthe hydrogen equivalents of the one or more curing agents and the epoxyequivalents of the one or more epoxy resins is not affected when addingfibres 1-4.

HEMPADUR PRO 45601-19870 is an anticorrosive epoxy paint from Hempel A/Sthat may be specified for ballast tanks. The epoxy-based binder systemof HEMPADUR PRO 45601-19870 consists of: Bisphenol A epoxy resins havingepoxy equivalent weights within the interval 150-700 and apolyamidoamine as curing agent. HEMPADUR PRO 45601-19870 furthermorecomprises aluminium pigment (the amount is within the interval 1-7% bysolids volume of the paint) and a modified aromatic hydrocarbon resin asplasticizer (the amount is within the interval 1-25% by solids volume ofthe paint). The viscosity is less than 140 KU at 30° C. The ratiobetween the hydrogen equivalents of the one or more curing agents andthe epoxy equivalents of the one or more epoxy resins is in the range of60:100 to 120:100. The ratio between the hydrogen equivalents of the oneor more curing agents and the epoxy equivalents of the one or more epoxyresins is not affected when adding fibres 1-4.

Intershield ENA300 is an aluminium pure epoxy anticorrosive paint fromInternational Marine Coatings Ltd. which is suitable for applicationover prepared shop primers. The paint can be specified to various areasincluding water ballast tanks. The epoxy-based binder system ofIntershield ENA300 consists of epoxy resins having epoxy equivalentweights within the interval 150-700 and a mannich base type adduct ascuring agent. The viscosity is less than 140 KU at 30° C. The ratiobetween the hydrogen equivalents of the one or more curing agents andthe epoxy equivalents of the one or more epoxy resins is in the range of60:100 to 120:100. The ratio between the hydrogen equivalents of the oneor more curing agents and the epoxy equivalents of the one or more epoxyresins is not affected when adding fibres 1-4. The total amount ofepoxy-based binder system is in the range of 35-80% by solids volume ofthe paint. The total amount of pigments and fillers is in the range of10-40% by solids volume of the paint.

HEMPADUR 45143-11480, HEMPADUR 15500-50900, HEMPADUR PRO 45601-19870 andIntershield ENA 300 added respectively 7.4% and 10.7% solids volume ofthe paint of fibres are suitable paint compositions according to theinvention. These paint compositions are very robust and can withstandthe corrosive environment of a ballast tank.

Methods

Preparation of Test Panels

Where not specifically stated elsewhere, the test panels used areapplied according to the procedure stated below.

Steel panels are coated with 2×150 μm (dry film thickness) of the paintto be tested by airless spraying with a recoat interval of 24 hoursbetween the two coats. The steel panels used are all cold rolled mildsteel, abrasive blasted to Sa 3 (ISO 8501-1), with a surface profileequivalent to BN 10 (Rugotest No. 3). After the samples have beencoated, the panels are conditioned at a temperature of 23±2° C. and50±5% relative humidity for a period of 7 days if not otherwise stated.

The Thermal Cycling Resistance Test

This method is conducted according to the Nace standard TG 260. It is anaccelerated thermal fatigue test, in which a coating is subjected tofast, and extreme temperature changes, thereby inducing thermal andmechanical fatigue within the coating. It is conducted in a programmabletemperature controlled oven, capable of reaching upper and lowertemperatures of +60° C. to −30° C., within a two hour time period. Thepanels used are steel panels in v-shape prepared by bending a steelplate (100×200×1.5 mm) 90° along the central axis lengthwise. An evenlayer of the paint composition is applied by airless spraying from a20-30 cm distance on to the surface representing the 90° angle, aimingto achieve an average dry film thickness of approximately 1000 μm. Themaximum dry film thickness which is obtained in the bottom of the V isstated for each of the paint compositions in the relevant tables. Thedistribution of the dry film thickness along the surface depends on howthe panel is Positioned during spray application and drying. Twovariants are used:

Variant A: The panel to be applied is placed so that each side of theV-shaped panel forms a 45° angle with horizontal.

Variant B: The panel to be applied is placed on a plate with one of thesides of the V-shaped panel in full contact with the plate and orientedhorizontally in respect of the earth.

The variant used appears from the relevant tables.

After coatings are applied, the panels shall be post cured at 60° C. forone week to dry out any volatile components before running the thermalcycling test. During drying and post curing, the panel is placed asduring application. At each inspection, the samples are removed to beexamined under microscope for any cracks in the coating.

The Tensile Strength Test

The test method is based on ASTM D 2370-92. It covers the procedure forassessing the relative elongation, the tensile strength, and thestiffness (modulus of elasticity) of a coating of paint, varnish orrelated product when tested as a free film and subjected to testing in atensile strength test machine under standard conditions. The tensilestrength test is performed on a Zwick Universal Testing MachineZ2.5/TN1S equipped with load cells of 50, 500, or 2500 N. The coating(2×150 μm dry film thickness) is applied on overhead foil which is cutinto test strips of 20×100 mm 24 hours after application of final layerof coating. The overhead foil is subsequently removed from the strips,leaving test strips of free coating film. After a sample has beenconditioned, it is clamped in the test machine sample holders. Onesample holder has a fixed position and the other is moved away at aconstant speed of 10 mm per min. The paint sample is elongated untilbreakage of the sample occurs, and the values of stress (force/area) andstrain (elongation) are recorded. The higher stress value the bettertensile strength, the higher elongation the more flexible. The procedureis repeated in triplicate for each of the test films made. The averageelongation until breakage is calculated. The average elongation for thereference composition without fibres is set to 100.

The Pull-Off Test

Pull-off test according to ISO 4624 (ASTM D 4541) with P.A.T hydraulicadhesion tester. This test covers the determination of the pull-offstrength of a coating or coating system, by determining the greatestperpendicular force (in tension) that a surface area can bear, before aplug of material is detached. Failure will occur along the weakest planewithin the system comprised of the test fixture, adhesive coating systemand substrate. After the panels have been coated and conditioned, asteel pin doll with a surface area of 1.58 cm² is glued onto the paintsurface on the test panel (150×200×1.5 mm) with Standard Araldit glue,cured for 24 hours. After curing of the glue, the paint film is cut freearound the dolls down to the substrate and the dolls are pulled offusing the P.A.T hydraulic adhesion tester. The pull-off value (tensilestrength) is noted, and converted in relation to the area of the dolland stated in MPa. The type of rupture is also noted(cohesive/adhesive). The pull-off value for the reference compositionwithout fibres is set to 100.

The Impact Test

Impact (effect of rapid deformation), according to ISO 6272-1,Falling-weight test, large-area indenter using an Erichsen ImpactTester. This test method covers a procedure for rapidly deforming byimpact a coating film and its substrate and for evaluating the effect ofsuch deformation. After the panels have been cured and conditioned, afalling-weight of 1 kg, with an indenter-head of 20 mm Ø, is dropped adistance onto the test panel (150×100×1.5 mm). The panel is supported bya steel fixture, with a hole of 27 mm Ø, centred under the indenter.When the indenter strikes the panel, it deforms the coating and thesubstrate. By gradually increasing the distance, the weight drops, thepoint at which failure usually occurs can be determined. The impactvalue is reported as the highest impact, reproduced 5 times, whichresults in no visible cracks and no adhesion failure in the paint film.The impact value is stated as kg·m (Joule). A possible rupture isevaluated as cohesive or adhesive.

Preparation of Test Paints

The base component of a commercial paint was thoroughly stirred, fibreswere added and the composition was mixed on a Diaf dissolver for 15minutes at 1,000 rpm to a homogenous mixture. Just before theapplication, the commercial curing agent was added and the paintcomposition was mixed to a homogenous mixture. The materials as well asthe ratios used appear from Tables 1-3. The results are shown in Tables4-11.

Composition of Test Paints

TABLE 1 HEMPADUR 45143-11480 Model paint A1 Amount Amount Amount (partsby (parts by (% solids wet weight) wet weight) volume) Hempadur Base81.9 81.9 (45148-11480) Hempadur curing agent 18.1 18.1 (97820-00000)Mixed product 100.0 100.0 92.6 Fibre 1 — — — Fibre 2 — — — Fibre 3 — — —Fibre 4 — 5.2 7.4 SVR 60.0 62.8* Epoxy-based binder 52.9 49.3 system %Solids Volume Pigments and fillers 26.9 25.0 % Solids Volume *Calculatedbased on measured value for HEMPADUR 45143-11480.

TABLE 2 HEMPADUR 15500-50900 Model paint B1 Amount Amount Amount (partsby (parts by (% solids wet weight) wet weight) volume) Hempadur Base93.8 93.8 (15509-50900) Hempadur curing agent 6.2 6.2 (97580-00000)Mixed product 100.0 100.0 92.6 Fibre 1 — 8.2 7.4 Fibre 2 — — — Fibre 3 —— — Fibre 4 — — — SVR 68.0 70.2* Epoxy based binder 59.0 54.6 system (%Solids Volume) Pigments and fillers 37.3 34.6 (% Solids Volume)*Calculated based on measured value for HEMPADUR 15500-50900.

TABLE 3 Hempadur Pro Model paint C1 Model paint C2 Model paint C3 Modelpaint C4 45601-19870 Amount Amount Amount Amount Amount (parts by Amount(parts by Amount (parts by Amount (parts by Amount (parts by wet (%solids wet (% solids wet (% solids wet (% solids wet weight) weight)volume) weight) volume) weight) volume) weight) volume) HEMPADUR PRO85.4 85.4 85.4 85.4 85.4 Base (45609-19870) Hempadur Pro 14.6 14.6 14.614.6 14.6 curing agent (97330-00000) Mixed product 100.0 100.0 89.3100.0 92.6 100.0 92.6 100.0 92.6 Fibre 1 — 15.4 10.7 — — — — — — Fibre 2— — — 5.6 7.4 — — — — Fibre 3 — — — — — 10.8 7.4 — — Fibre 4 — — — — — —— 5.2 7.4 SVR 66.0 69.3* 68.3* 68.3* 68.3* Epoxy based binder 51.6 46.147.8 47.8 47.8 system (% Solids Volume) Pigments and fillers (% 28.525.4 26.3 26.3 26.3 Solids Volume) *Calculated based on measured valuefor HEMPADUR Pro 5601-19870.

Results

Results of Tensile Strength Test

TABLE 4 HEMPADUR 45143-11480 Model paint A1 Elongation at break 100 12125° C. Elongation at break 100 117 60° C.

TABLE 5 HEMPADUR 15500-50900 Model paint B1 Elongation at break — — 25°C. Elongation at break 100 162 60° C.

Results of the Thermal Cycling Resistance Test

Commercial products like HEMPADUR 15500-50900, HEMPADUR PRO 45601-19870and Intershield ENA300 are not sensitive to cracking when appliedaccording to specification but a higher flexibility is required if theproducts are applied in extreme high dry film thickness like 1000 μm orabove.

TABLE 6 Maximum dry film HEMPADUR thickness: 5500-6200 μm* 15500-50900Model paint B1 After 13 cycles Cracking No cracking *Positioning ofpanel during spray application and drying: variant A.

TABLE 7 maximum dry film thickness: HEMPADUR PRO 1600-2200 μm*45601-19870 Model paint C1 Model paint C2 Model paint C3 Model paint C4After 13 cycles Cracking No cracking No cracking No cracking No cracking*Positioning of panel during spray application and drying: variant B.

Results of the Pull-Off Test

TABLE 8 Paint Composition Pull-off value HEMPADUR 45143-11480 100 Modelpaint A1 100 HEMPADUR15500-50900 100 Model paint B1 95 HEMPADUR PRO45601-19870 100 Model paint C1 98

The results show that the good adhesion between the layers and the highstrength within each layer is maintained at the same high level afterfibres are added.

TABLE 9 Intershield ENA300 Model paint D1 Model paint D2 Amount AmountAmount Amount Amount (parts by (parts by (% solids (parts by (% solidswet weight) wet weight) volume) wet weight) volume) ENA 300 78.3 78.378.3 Base ENA 303 21.7 21.7 21.7 curing agent Mixed product 100.0 100.092.6 100.0 92.6 Fibre 1 — 10.7 7.4 — — Fibre 2 — — — — — Fibre 3 — — —11.3 7.4 Fibre 4 — — — — — SVR 60 61.8* 61.8* Epoxy based binder 73.1% ±5%** 67.7 ± 5%** 67.7 ± 5%** system (% solids volume) Pigments andfillers 24.4% ± 5%** 22.6 ± 5%** 22.6 ± 5%** (% solids volume)*Calculated based on value stated on datasheet. **Calculated based oncomposition determined by analysis of the product.

Results of the thermal cycling resistance test

TABLE 10 Maximum dry film Intershield thickness: * 400-550 ENA300 Modelpaint D1 Model paint D2 After 192 cycles No cracking No cracking Nocracking After 252 cycles Cracking No cracking No cracking After 384cycles Cracking No cracking No cracking After 500 cycles Cracking Nocracking No cracking * Positioning of panel during spray application anddrying: variant A

Exposing an epoxy coating to 200 or more cycles in the thermal cyclicresistance test is a very demanding test. Typically a commercialproduct, e.g. HEMPADUR PRO 45601-19870, will start cracking after 200 to250 cycles at specified dft. The test can be used to establish therelative level of cracking resistance even when the coating is appliedin a total dry film thickness of only 250-500 μm (typical dft specifiedfor ballast tank coatings).

Results of the Impact Test

TABLE 11 Paint Composition Impact value Intershield ENA300 45 Modelpaint D1 60 Model paint D2 55 Hempadur Pro 45601 50 Model paint C4 60Hempadur 45143 40 Model paint A1 50

What is claimed is:
 1. A paint composition comprising: 0.5%-30% bysolids volume of the composition of one or more mineral fibers, said oneor more fibers having an average length of at most 250 μm; and 35-80% bysolids volume of the composition of an epoxy-based binder system havinga ratio between hydrogen equivalents and epoxy equivalents in the rangeof 60:100 to 120:100, the system comprising: a) one or more epoxy resinsselected from the group consisting of bisphenol A, bisphenol F andNovolac, and b) one or more curing agents selected from the groupconsisting of alkylene amines, aralkylamines and polyamines, and adductsand derivatives thereof, wherein the composition has a viscosity of atmost 140 KU at 30° C.
 2. The paint composition according to claim 1,wherein the one or more curing agents is a polyamine.
 3. The paintcomposition according to claim 1, wherein the one or more curing agentsis an alkylene amine.
 4. The paint composition according to claim 1,wherein the one or more curing agents is an aralkylamine.
 5. The paintcomposition according to claim 1, wherein the one or more epoxy resinshave an epoxy equivalent weight of 100-1500.
 6. The paint compositionaccording to claim 1, wherein the one or more fibers have an averagelength of 50-170 μm and a ratio between the average length and theaverage thickness of at least
 2. 7. The paint composition according toclaim 1, wherein the one or more fibers have an average thickness of1-50 μm.
 8. The paint composition according to claim 1, wherein the oneor more fibers have an average thickness of 2-10 μm.
 9. The paintcomposition according to claim 1, further comprising 10-45% by solidsvolume of the composition of fillers and pigments; 0-30% by solidsvolume of the composition of plasticizers; and 0-10% by solids volume ofthe composition of additives.
 10. A method for protecting a surface fromenvironmental effect(s), the method comprising: applying the paintcomposition according to claim 1 to the surface; and allowing saidcurable paint film to cure, thereby forming the epoxy paint coat on thesurface to protect the surface from the environmental effect(s).
 11. Themethod according to claim 10, wherein the environmental effect isselected from the group consisting of elevated temperature, impact fromheavy loading equipment, and hydrostatic pressure change.
 12. A methodfor the establishment of a crack resistant coating at the interiorsurface of a liquid storage tank, said method comprising: applying thepaint composition according to claim 1 onto the surface of the interiorof a liquid storage tank thereby forming a curable paint film on saidsurface; and allowing said curable paint film to cure thereby formingthe epoxy paint coat.
 13. A crack resistant coating formed by curing acomposition, the composition comprising: 0.5%-30% by solids volume ofthe composition of one or more mineral fibers, said one or more fibershaving an average length of at the most 250 μm; and 35-80% by solidsvolume of the composition of an epoxy-based binder system having a ratiobetween hydrogen equivalents and epoxy equivalents in the range of60:100 to 120:100, the system comprising: a) one or more epoxy resinsselected from the group consisting of bisphenol A, bisphenol F andNovolac, and b) one or more curing agents selected from the groupconsisting of alkylene amines, aralkylamines and polyamines, and adductsand derivatives thereof, wherein the composition has a viscosity of atthe most 140 KU at 30° C.
 14. A liquid storage tank comprising aninternal surface, said liquid storage tank covered on at least part ofsaid internal surface by the crack resistant coating of claim
 13. 15. Aballast tank comprising an internal surface, said at least part of saidinternal surface is covered by the crack resistant coating of claim 13.16. The ballast tank of claim 15, further comprising at least one firstplate and at least one second plate arranged at an angle of between 45°to 140° to the first plate; wherein the angle is coated with the crackresistant coating.
 17. A vessel comprising at least one liquid storagetank according to claim 14 and/or at least one ballast tank according toclaim
 15. 18. The paint composition according to claim 1, wherein theratio between the hydrogen equivalents of the one or more curing agentsand the one or more epoxy resins is in the range of 70:100 to 110:100.